OFFSET
1,1
LINKS
Chai Wah Wu, Table of n, a(n) for n = 1..52
Armin Straub, On congruence schemes for constant terms and their applications, arXiv:2205.09902 [math.NT], 2022. see Theorem 3.3 p. 13.
PROG
(PARI) catalan(n) = binomial(2*n, n)/(n+1);
M(n) = sum(k=0, n, (-1)^(n-k)*binomial(n, k)*catalan(k+1));
a(n) = {my(p=prime(n)); if (p>200, error); if (vecsearch([5, 13, 31, 37, 61, 79, 97, 103], p), return (-1)); my(k=1); while (M(k) % p^2, k++); k; };
CROSSREFS
KEYWORD
sign
AUTHOR
Michel Marcus, May 23 2022
EXTENSIONS
a(16)-a(38) from Daniel Suteu, May 23 2022
a(39)-a(47) from Chai Wah Wu, May 23 2022
STATUS
approved